1. Field of the Invention
The invention relates to a pressure limiting valve and more particularly to an improved pressure limiting valve suitable for use fuel injection systems.
2. Description of the Prior Art
A pressure limiting valve in conjunction with a device for injecting fuel, in particular Diesel fuel, is known from the book entitled Diesel-engine Management, Stuttgart 1999, page 273 (ISBN 0-7680-0509-4). A pressure limiting valve of this type serves to limit pressure yet at the same time furnish an emergency operation capability. Preferably, the pressure limiting valve of this type is used in conjunction with common rail systems.
Mass-produced pressure limiting valves are already known in which spring washers and valve pistons are embodied in one piece and disposed together with a compression spring in a cup-shaped valve holder. On its end piece remote from the valve piston, the valve holder has an adjusting screw with a check nut, by way of which the valve characteristic can be adjusted and production variations can also be compensated for. Aside from the complicated and expensive construction, these known valves require a relatively large installation volume, which makes it difficult to integrate them into component groups of an injection system. Moreover, these known valves have the disadvantage of regulating down to a pump feeding quantity of only about 90 liters/hour. At a lower flow rate, such a pressure limiting valve closes again. However, this causes severe restrictions in emergency operation.